Limb alignment and kinematics inside a Lokomat robotic orthosis

The use of robotic gait training systems has become commonplace world-wide. In particular, the Lokomat robotic orthosis (Hocoma AG, Volketswil, Switzerland) is in use at nearly 75 facilities treating patients with spinal cord injury, stroke, and other neurological impairments. Despite the extensive use of the device, no studies have reported the leg kinematic trajectories while walking in the device. Furthermore, because the subject's legs are not rigidly coupled to the device, there is the potential for significant leg movement inside the device which also has not been reported. Here we report differences in kinematic trajectories between walking in the Lokomat and walking on a treadmill, as well as the relative limb motion within the Lokomat for a single representative subject. Using high-speed motion analysis, it was found that while similar knee and hip angle patterns were produced when walking on the treadmill and while walking in the Lokomat, there were significant differences (p<.0.01) in percent time spent in swing phase, maximum hip and knee flexion, and maximum hip extension. There was also a larger amount of misalignment at the hip (18.2 mm) than at the knees (12 mm) when the joint positions in space were compared.